Antibacterial activity of essential oil obtained from Origanum majorana L. by solvent-free microwave extraction

With the increasing demand for the use of volatile oils in the pharmaceutical and food industries, an efficient “green” extraction method for isolation of essential oils (EOs) from plant materials has become important. Solvent-free microwave extraction (SFME) is a new technique which combines microwave heating with dry distillation at atmospheric pressure for the isolation and concentration of the EOs from plant materials[1,2]. The objective of this study was to compare the SFME and conventional hydrodistillation (HD) processes for Origanum majorana L. and to characterize the resulting EO for their chemical constituents using GC/MS and antibacterial properties against a marker organisms (Table 1).

Table 1. Antimicrobial activity of Origanum majorana L. EOs. againts the bacterial strains tested by the disc diffusion method.

a P=Penicillin G (10 units); VA=vancomycin (30µg); AMC=amoxicillin/clavulanic acid 2:1 (30µg); CAZ=ceftazidime (30µg); MEM=meropenem (10µg); and FEP=cefepime (30µg).
Bacterial species	SFME, mm	HD, mm	Antibiotic control, mma	Negative contol
S.aureus ATCC 25923	28	29	35(P)	-
P.aeruginosa ATCC 27853	9	9	27(MEM)	-
E.coli ATCC 25922	29	30	19(AMC)	-
K.pneumoniae ATCC13883	21	21	24(CAZ)	-
S.marcescens ATCC 8100	18	19	32(MEM)	-
E.faecalis ATCC 29212	12	15	21(VA)	-

[1] Sozmen. F, Uysal. B, Oksal. B.S, et al. (2011)J. AOAC Int., 94:243–250, [2] Uysal. B, Sozmen. F, Aktas. O, Oksal. B.S, Kose, E.O (2011) Int. J. Food Sci. Tech., 46:1455–1461